The present invention relates to a recording sheet finishing apparatus for automatically conducting the stapling operation by a stapler on recording sheets, on which images are recorded by an image forming apparatus, and after stapling, the recording sheets are delivered from the finishing apparatus. Specifically, the present invention relates to a recording sheet finishing apparatus appropriate for an image forming apparatus in which high speed processing can be conducted.
A recording sheet finishing apparatus, which is called a finisher, is used as an apparatus by which a plurality of recording sheets, on which images have been recorded and which are delivered from the image forming apparatus, are collated and stapled for each copied volume.
This finisher is connected with the image forming apparatus main body in terms of function, and is driven in correspondence with sequential operations of the copying processes.
Accordingly, with respect to the image forming apparatus which can conduct the copying processes at high speed, a finisher, which can perform its function at the correspondingly high speed of the image forming apparatus, is necessary.
Concerning the finisher which can carry out the copying processes at a high speed, various proposals have been made in the following publications: Japanese Patent Publication Open to Public Inspection No. 142359/1985, No. 158463/1985, No. 239169/1987, No. 288002/1987, No. 267667/1988, and No. 276691/1990; and Japanese Patent Publication No. 41991/1993. In these proposals, since only one stapler is provided or only one delivery tray is provided in the finisher, the processing speed can not be greatly increased. Specifically, in the first two publications, since a function in which a bundle of recording sheets stacked on two intermediate trays being collated, are conveyed to one stapler placed at another position, is necessary, the structure becomes complicated, and additional operations are required, which is disadvantageous.
When a bundle of recording sheets, stacked and aligned on the stacker so that one end of the recording sheets are aligned with one end of the stacker which is used as the reference for aligning the recording sheets, are conveyed by a delivery belt, positions of the center of gravity of bundles of recording sheets are different from each other due to sizes of the recording sheets. Accordingly, when the delivery belt does not include the position of the center of gravity of the bundle of recording sheets, the bundle of sheets is inclined and conveyed, resulting in sheet delivery errors. When the delivery belt is composed of one broad belt, the conveyance mechanism is complicated, belt driving loads are increased, or the manufacturing cost is increased, and these become serious problems in high speed delivery and cost.
Further, when delivery trays such as a non-sort tray or an offset tray on which non-stapled sheets are stacked after delivery and a large number of sheets can be stacked, and at least one delivery tray on which bundles of stapled sheets are stacked, are separately provided, then, the number of delivery trays is increased, and delivery trays and driving mechanisms are further complicated, so that the apparatus becomes larger, which is also disadvantageous.
Further, when a large number of sheets are stapled into a bundle of sheets, a sheet stacked close to the final sheet can not arrive at the stop position of the stacker, so that all the sheets occasionally can not be stapled accurately.